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Title:
SYSTEM FOR THE TREATMENT OF THE COMBUSTION PRODUCTS
Document Type and Number:
WIPO Patent Application WO/2019/048920
Kind Code:
A1
Abstract:
The object of the present invention is a system (1) for the treatment of the fumes (F) produced by the combustion of a combustible material in a combustor and comprising at least one stage (2) for the cleaning and purification of said fumes (F) from suspended pollutants, such as dusts and/or particulates and/or micropollutants or the like. Said stage (2) comprises in series at least one loading zone (20) adapted to receive at least said combustion fumes to be treated and a washing zone (22) in which said cleaning and purification of said fumes (F) is carried out by means of their interaction with a washing fluid (A), said loading zone (20) being set up to receive at least part of the ash (C) produced by the combustion of said combustible material.

Inventors:
USCI ROSALINO (IT)
MARCANTONI MICHELE (IT)
Application Number:
IB2018/000943
Publication Date:
March 14, 2019
Filing Date:
August 24, 2018
Export Citation:
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Assignee:
TRE P ENG S R L (IT)
International Classes:
F23J15/04
Domestic Patent References:
WO2013039067A12013-03-21
WO2017010870A12017-01-19
Foreign References:
GB2205766A1988-12-21
DE102015212893A12016-01-14
EP1889649A22008-02-20
Attorney, Agent or Firm:
PREMRU, Rok (2 Via San Filippo, Fabriano, IT)
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Claims:
CLAIMS

System (1) for the treatment of fumes (F) produced by the combustion of a combustible material in a combustor comprising at least one stage (2) for the cleaning and purification of said fumes (F) from suspended pollutants, such as dusts and/or particulates and/or micropollutants or the like, said stage (2) in turn comprising in series at least:

- a loading zone (20) adapted to receive at least:

- said combustion fumes to be treated,

- ash (C) produced by the combustion of said combustible material, said ash (C) acting as condensation nuclei of the vapours of said fumes (F),

- a mixing zone (21) of said fumes (F) and said ash (C), said fumes (F) and ash (C) defining a fume-ash mixture (F+C)

- a washing zone (22) in which an interaction between a washing fluid (A) and said fume-ash mixture (F+C) crossing it is carried out, said washing fluid (A) capturing and reducing said pollutants of said fumes (F) and hydrating said ash (C),

characterised in that said washing fluid (A) in said washing zone (22) is at least one cylinder of washing fluid and/or at least one blade of washing fluid, said at least one cylinder and/or blade of washing fluid intercepting and intersecting said mixture (F+C).

System (1) according to claim 1,

characterised in that said ash (C) is introduced in said loading zone (20) with a whirling-turbulent motion that eases and favours the reciprocal collision among ash particles and/or with those said pollutants suspended in said fumes (F) and/or with the walls of said loading zone (20) and the consequent further crushing and pulverisation thereof, said crushing and pulverisation increasing the number of said condensation nuclei.

System (1) according to claim 1 and/or 2

characterised in that said ash (C) are intentionally introduced in said loading zone (20), said ash (C) being drawn from appropriate temporary storage sites of said system (1) and/or combustor.

System (1) according to any previous claims,

characterised in that said mixing zone (21) is placed between said loading zone (20) and said washing zone (22) by which it is in fluid communication, a pre-hydration of said ash (C) being able to be carried out in said mixing zone (21).

System (1) according to any previous claims excluding 4,

characterised in that said mixing zone (21) is comprised and integrated in said loading zone (20), a pre-hydration of said ash (C) being able to be carried out in said mixing zone (21).

System (1) according to any previous claims,

characterised in that said washing zone (22) comprises a decantation tank (23) for the collection of washing residues and of said ash (C), the hydration of said ash (C) being able to be completed in said tank (23).

System (1) according to any previous claims,

characterised in that said first loading zone (20) comprises a first duct

(200) capable of being crossed by said combustion fumes (F) and a conveying chamber (201) adapted to receive at least said ash (C), said conveying chamber (201) comprising at least one inlet (202) for said ash (C).

System (1) according to the previous claim,

characterised in that said first duct (200) and said conveying chamber

(201) are coaxial to each other, said conveying chamber (201):

- being external and crossed by said conduit (200),

- having truncated-cone geometry along its longitudinal development,

- comprising a converging portion between its summit zone and a discharge outlet (205) thereof towards the said next mixing zone (21).

System (1) according to any claims,

characterised in that said washing zone (22) comprises an inner space (220) comprised between: - side walls (221),

- a bottom (222) communicating with said decantation tank (23).

- an upper cover (223) cooperating with an overlying inlet chamber (224) for said washing fluid (A), said chamber (224) comprising at least one inlet (225) for said washing fluid (A),

said space (220) being crossed in equicurrent, from top to bottom, by said mixture (F+C) of fumes and ash and by said washing fluid (A).

10. System (1) according to the previous claim,

characterised in that said cover (223) comprises at least one slit (228) for the passage of said washing fluid (A) from said inlet chamber (224) to said inner space (220), said at least one slit being able to consists of at least one circular slit capable of generating the above-mentioned at least one cylinder of washing fluid.

11. System (1) according to the previous claim,

characterised in that said at least one slit (228) consists of a plurality of circular and concentric slits, said slits generating concentric washing fluid cylinders.

12. System (1) according to claim 9,

characterised in that said cover (223) comprises a plurality of slits (228) shaped as slots capable of generating the above-mentioned blades of washing fluid.

13. System (1) according to any previous claims,

characterised in that said at least one inlet (225) for the washing fluid (A) in said inlet chamber (224) of the washing zone (22) and said at least one inlet (202) of said ash (C) in said conveying chamber (201) of the loading zone (20) are tangential, said tangential inlets imparting whirling motions to said washing fluid (A) and to said ash (C).

14. System (1) according to the previous claim,

characterised in that said swirling motions have directions of rotation opposite to each other. System (1) according to any previous claims,

characterised in that said stage (2) comprises a loading section (227) of the fumes treated and intended for further treatment and/or direct disposal into the atmosphere.

System (1) according to any previous claims,

characterised in that said combustible material is poultry dejection.

Method for the treatment of fumes (F) produced by the combustion of a combustible material in a combustor implementable within at least one stage (2) of the treatment system (1) according to one or more claims 1 to 16 and suitable for the cleaning and purification of said fumes (F), said fumes (F) containing suspended pollutants such as dusts and/or particulates and/or micropollutants or the like and vapours,

characterised in that at least part of the ash (C) produced by said combustion of said combustible material is introduced into said stage (2), said ash (C) acting as condensation nuclei of said vapours of said fumes (F) and being capable of being hydrated.

Description:
SYSTEM FOR THE TREATMENT OF THE COMBUSTION PRODUCTS

D E S C RI P T I O N

The present invention relates to a system for the treatment of fumes produced by the thermo-valorisation of rejection or waste material.

More precisely, the object of the present invention is a system for the treatment of the fumes produced by the thermo-valorisation of biomasses, preferably animal effluents, such as poultry dejections, available from farms.

A further object of the present invention is a system for the treatment of fumes produced by the thermo-valorisation of rejection or waste material capable of "valorising" ash produced by said thermo-valorisation.

As known, the term "thermo-valorisation" refers to the controlled combustion process of rejection material or waste, both of organic origin and not, aimed at recovering their energy content and producing electrical and or thermal energy.

The currently known waste-to-energy plants are complex technology systems, equipped with sophisticated control systems and efficient environmental controls. Usually, they include at least:

- a receiving and storage stage of said rejection materials or waste and for the introduction into a combustor,

- said combustor that represents, in its many currently existing executive and construction embodiments, the heart of the plant wherein the combustion of said rejection materials or waste is carried out with the consequent formations of fumes, ash and combustion by-products,

- energy recovery systems for the production of said thermal and/or electric energy

- a fume treatment stage wherein the combustion gases and fumes exiting the combustor are subjected to a series of treatments aimed at the removal of pollutants (dusts, acid gases, micropollutants and nitrogen oxides) for being expelled into the atmosphere with negligible concentration values compared to those permitted by the environmental regulations.

Very often, said combustion fume treatment stage comprises at least one Venturi scrubber possibly connected, downstream, with a second scrubber (also known as "washing tower") for the removal of dust residues and micropollutants (e.g., hydrochloric acid, sulphur dioxide and/or ammonia residues) not captured and retained therein.

As is known, in a typical Venturi scrubber the flow of combustion fumes containing gas, particulate and/or polluting particles is progressively accelerated along a convergent portion thereof while in proximity or at its groove a washing fluid (usually water) is introduced in a turbulent manner, for example by means of atomisation or nebulisation systems (usually, one or more spray nozzles). In said groove, the liquid atomised in very fine droplets acts as an impact nucleus for the polluting dusts of the fumes, capturing and retaining them definitively.

The next divergent portion allows slowing down the flow facilitating the precipitation in a tank for collecting the drops loaded with the pollutants subtracted from the fumes.

It is known that the efficiency in capturing dusts and particulate increases with increasing speed of the flow and turbulences of the combustion fumes in the groove; obtaining an optimal speed, however, is a very complex and delicate operation requiring considerable design and dimensioning efforts of at least the convergent portion and the groove of the Venturi scrubber.

Even the right flow rate of washing liquid to be introduced into the Venturi scrubber is a very difficult parameter to define and set; in general, a quantity of liquid proportional to the flow rate of the fumes to be treated must be injected, taking into account also the possible reintegrations necessary to obviate evaporation phenomena, especially in presence of very hot fumes.

Often the quantity of injected washing liquid is not sufficient in relation to the flow rate of the fumes to be treated and their level of pollution, with unsatisfactory cleaning results.

Equally frequently, said fumes leave the treatment and purification system still particularly humid with the consequent risk of acid corrosion and condensation to the stack for discharge into atmosphere or in any equipment and components placed downstream.

Said waste-to-energy plants are increasingly used also for the combustion of organic biomasses, both vegetable and animal.

As known, the term "biomass" refers to the biodegradable fraction of products, waste and residues of biological origin coming from agriculture, forestry and related processing industries and from animal farms as well as the biodegradable part of industrial and urban waste.

A particular and peculiar field of application of such waste-to-energy plants can be that of the combustion of poultry biomasses, i.e., of poultry dejections (also known, in jargon, with the term "manure").

In this case, the treatment and purification stage of fumes and products deriving from their combustion may include additional components and devices to the Venturi scrubber and/or to the washing tower.

More particularly, the chemical-physical characteristics of said dejections may require the use of at least: a "urea-ammonia conversion chamber", a dedusting system (e.g., a cyclone possibly connected to a bag filter) and a possible selective catalytic reduction system.

Since the aforesaid components are well known to the man skilled in the art, it is not necessary to dwell to much on their technical features and related operation. Here it is sufficient to highlight that the presence of a high number of components and devices for cleaning and filtering combustion fumes, interconnected and cooperating with each other, leads to an increase in the construction and installation complexity of a waste-to-energy plant, as well as to higher ordinary and/or extraordinary maintenance costs (spare parts, assistance interventions by external firms, etc.). Some of said devices may also have rather considerable overall dimensions (suffice it to mention that the aforesaid "bag" filter, when present, may have filtering surfaces of even some tens of m 2 ) which may limit its use, especially in environments with limited space availability.

A second negative aspect very popular in the waste-to-energy plants of rejection materials, waste or biomasses concerns the collection and disposal of solid combustion residues, e.g, of the combustion ash and dusts.

The disposal in landfill of such ash, which can be rich in pollutants and heavy metals, is not, for example, always possible without preliminary and costly depuration and/or decontamination treatments.

Such issue is even more felt in the thermo-valorisation of poultry dejections, the latter being in fact characterised by a high copper content due to the diets and feed used for animal nutrition.

Their decontamination treatments and transport to landfill may therefore be particularly complex and costly.

Moreover, the transport of ash to be disposed of, usually particularly "dry" and dusty, may be very critical, with the risk of spreading and dispersion in the surrounding environment and into the atmosphere.

It is also true that very often combustion ash can be rich in substances and compounds that can be re-used for other purposes, thus making their disposal in landfills disadvantageous and unsuccessful.

For example, poultry dejections or other biomasses (such as wood, mowings or similar agricultural or livestock products and by-products) may contain large quantities of nitrogen, phosphorus and related compounds that can make the relative combustion ash resources; for example and without any limiting intent, usable in the production of fertilisers.

However, this requires a series of complex operations and preparatory work, well known to those skilled in the art, as well as expensive and dedicated equipment capable of implementing them. In particular, particular attention is required for the hydration step of said ash, for example by means of water jets or suitable liquid solutions.

It may happen that said ash have a "size" and a particularly coarse particle granulometry with the consequent risk, during the hydration operation, of formation of large clumps and thickenings, especially if the water flow rate has not been chosen and sized correctly; the formation of such lumps could slow down the hydration process itself as well as lead to the need of providing, downstream, operations of "breaking" the same clumps and thickenings.

Furthermore, said clumps and thickenings could cause encrustations and/or breakages or malfunctions of moving mechanical members, for example the blades of pumps or conveyor screws.

The use of special equipment for reusing such ash has a negative impact on the production, installation and management costs of said plants for the thermo- valorisation of rejection materials and waste and/or biomasses.

The main object of the present invention is to obviate the aforementioned drawbacks, by providing a system, and relative method, for the treatment of the products and fumes deriving from the combustion of rejection materials and/or waste and/or biomasses capable of minimizing the polluting emissions and the dispersion into the atmosphere of dustlike and contaminating material.

A second object of the present invention is to provide a system for the treatment of combustion fumes of rejection materials and/or waste and/or biomasses that ensures a considerable reduction of their absolute humidity.

A further object at least for some variants of the present invention is to provide a system for the treatment of the combustion products and fumes of rejection materials and/or waste and/or biomasses with a reduced number of components, reduced overall dimensions and high efficiency and inexpensiveness.

A further object at least for some variants of the present invention is to provide a system for the treatment of the combustion products and fumes of a plant for the thermo-valorisation of rejection materials and/or waste and/or biomasses capable of "valorising" and recovering for other uses the ash produced by said combustion. These and other objects, which will become clear later, are achieved with the system for the treatment of the combustion products and fumes of waste materials and/or waste and/or biomasses disclosed in the following description and in the annexed claims, which constitute an integral part of the same description.

Further features of the present invention shall be better highlighted by the following description of a preferred embodiment, in accordance with the patent claims and illustrated, purely by way of a non-limiting example, in the annexed drawing tables, in which:

- Fig. 1 shows an axonometric view of the system for the treatment of the combustion products and fumes that incorporates the invention;

- Fig. 2 is a top view of the system for the treatment of combustion products and fumes of Fig. 1 ;

- Fig. 3 is a view according to section A-A of the system for the treatment of combustion products and fumes of Fig. 1 and 2;

- Fig. 4a shows, in axonometry, a component of the system for the treatment of combustion products and fumes of the invention, while Fig. 4b is a section view thereof;

- Figs. 5a, 5b and 5c respectively show a front, top and section B-B view of the component of Fig. 4a, 4b;

- Fig. 6 schematically shows details of a component of the system for the treatment of the combustion products and fumes of the invention;

- Fig. 7 shows an executive embodiment of a waste-to-energy plant for waste material, waste and/or biomass employing the system for the treatment of combustion products and fumes of the invention.

Unless otherwise specified, in this report any possible absolute spatial reference such as the terms vertical/horizontal or lower/upper, previous/next, upstream/downstream refers to the position in which the elements are arranged in operating conditions.

With the purpose of highlighting some features instead of others, not necessarily what described in the annexed drawings is to scale.

With reference to the drawings attached to the present disclosure, 1 indicates the system for the treatment of products and fumes deriving from the combustion of any rejection or water material or biomass.

Without any limiting intent, said system 1 is particularly suitable for the treatment of biomass combustion fumes, for example poultry dejections.

Nothing obviously prevents the possibility of adapting, except for minimum component and constructive adjustments within the reach of the man skilled in the art, its use to the treatment of combustion products and fumes of any other type of animal or vegetable biomass, as well as any other rejection or waste material having same or equivalent compositions and chemical-physical characteristics.

This is to say that said system 1 for the treatment of the combustion products and fumes that will be described may be suitable without distinction for the treatment of any rejection material or product with at least a high content of Nitrogen and/or Phosphorus and/or Sulphur and/or Chlorine and/o heavy metals and/or compounds thereof and an even very high degree of humidity of the fumes produced, up to saturation; said substances and compounds being found in the relative combustion products, both gaseous and solid, such as gases, combustion fumes and/or ash.

For the sake of simplicity, said rejection materials, waste, biomasses or the like hereinafter will be referred to as "combustible material".

As in the plants of the prior art, even the system for the treatment of combustion products and fumes 1 of the invention is normally positioned and installed between at least one combustor of combustible material and a stack for discharge into the atmosphere of the treated fumes.

Without loss of generality said combustor may be of known type and normally used in the waste-to-energy plants already installed and operating or, according to a possible embodiment, of the type already described in the patent application No. 102017000015695 in the name of the same Applicant, to which reference is made for any further analysis and shown with the reference COMB in Fig. 7 attached to the present disclosure.

In general, said system 1 for the treatment of combustion products and fumes allows reducing the concentration of pollutants, such as powders, particulates and micro-pollutants, present in a gaseous stream.

For this purpose, the treatment system 1 may comprise at least one stage 2 intended for the removal of the particulate and the dusts carried in the fumes produced by the combustion of combustible material.

Said stage 2, preferably, may consist of a "wet-wall scrubber" 2 comprising in series:

- a "loading zone" 20 adapted to receive at least the combustion fumes to be treated,

- a "washing" zone 22, downstream, wherein the cleaning and purification of said fumes is carried out through their interaction with a washing fluid.

Preferably, said stage 2 may further comprise a "mixing" zone 21, the presence whereof and the relative object will be shortly understandable, placed between said loading 20 and washing 22 zone, with which it is in fluid communication. Alternatively, nothing prevents that in a simplified variant said mixing zone 21 is comprised and/or integrated in said loading zone 20 (in other words, the loading 20 and the mixing 21 zone may substantially coincide).

Said washing fluid may consist of washing water A, in the liquid or nebulised state, and is introduced into the washing zone 22 in order to:

reduce, "by capturing them" in a known manner, the particulate and the particles of dust and pollutants carried by the combustion fumes, and

- cool the combustion fumes themselves, contributing to the condensation of at least part of their humid component.

The washing fluid together with the particulate, the pollutants and the humid component subtracted from the flow of combustion fumes (hereinafter referred to as "washing residues") are normally collected, by gravity, in a decantation tank 23 placed on the bottom of said washing zone 22. A peculiar aspect of the wet-wall scrubber 2 of the present invention is the introduction into the loading zone 20 of part of the ash C produced by the combustion of the combustible material, which is then intended to mix with the fumes F in the mixing zone 21.

It is useful to specify that said ash C are on purpose and intentionally introduced in said loading zone 20 and can be added to those already potentially carried as a suspension, although in small quantities, by the combustion fumes.

In this regard, said ash C can be drawn from appropriate temporary storage sites, for example by containment spaces and/or storage areas of the system 1 of the invention and/or of the combustor wherein it is actually produced.

This mixing leads to the formation of a fume-ash mixture F+C.

Preferably, said ash C, suitably drawn and intentionally injected in said loading zone 20, are introduced with a swirling-turbulent motion so as to ease the mutual impact among their particles, which could also be of large dimensions and/or diameters, and possibly with those of the particulate already suspended in the fumes F and/or with the inner walls defining the loading zone 20.

This turbulent motion therefore contributes to causing and favouring the crushing and pulverisation of said ash C into particles of smaller dimensions. Basically, the voluntary insertion of ash C in the loading zone 20 and the swirling-turbulent motion thereto transmitted (in addition to those usually carried by the fumes) lead to a more "intimate" mixing and to a considerable increase in the number of condensation nuclei in the flow of combustion fumes, ensuring a more effective and complete removal of the gaseous humid component (vapours such as at least water vapour) and therefore a more "boosted" dehumidification thereof.

In fact, said nuclei act as condensation points of the vapours contained in the combustion fumes

From here on "condensation nuclei" are therefore to be intended as strongly hygroscopic microparticles of various nature, i.e. having affinity with vapours (e.g., water vapours); among these there can obviously be included those polluting particles suspended in the combustion fumes F already well before the addition of the above-mentioned ash C.

Said combustion fumes F therefore have an absolute humidity when exiting from the wet-wall scrubber 2 of the invention much lower than the inlet one.

In fact, as anticipated, the ash further reduced in volume act as condensation nuclei contributing to reducing the absolute humidity of said fumes. Experimentally, a reduction comprised between 30% and 80%, in particular of 50% was observed.

As a result of said interaction with the humid fumes, said ash C may be subject, already in the mixing zone 21, to at least a first partial hydration process (pre- hydration), which as seen in the description of the state of the prior art is necessary for a possible subsequent alternative use thereof, for example for the production of fertiliser.

The greatest contribution to said hydration of the ash C, however, occurs in the subsequent washing zone 22 of said scrubber 2 by the effect of the "boosted" interaction with the washing fluid A and can be completed in the underlying decantation tank 23 where it precipitates by gravity and inertia and collects in the form of sludge together with other washing residues.

During the hydration step in the washing zone 22, the ash particles C remain dispersed and suspended with a substantially null risk of forming large agglomerates and masses which would make, as seen, any subsequent preparation operations more problematic to an alternative use.

It is therefore evident that, unlike the prior art, the operation of hydrating the ash C does not need dedicated devices and equipment, exploiting the same scrubber 2 for the cleaning of the combustion fumes; this considerably simplifies the design and installation of the relative plants and speeds up the conversion and transformation processes of said ash C and its use in other fields. In particular, with respect to other known systems, the present ash treatment device is extremely compact.

Finally, at the outlet of the wet- wall scrubber 2 of the invention, there are obtained:

- substantially dedusting combustion fumes, with a very low content of pollutants and very low absolute humidity,

- ash in the form of sludge already substantially ready for being used in known transformation processes that make it compatible for an alternative use, for example as fertilisers.

Specific drawing means 7 (e.g., the discharge valves or gates 7 of Fig. 1 and/or 3) allow the emptying of at least the decantation tank 23 of the scrubber 2 and the drawing of said sludge.

While the loading zone 20 of the fumes F and/or of the ash C is, upstream, in fluid communication with the combustor (see for example the reference COMB in the schematic configuration of the plant in Fig. 7), the washing zone 22 may be connected, in outlet, directly with a stack for the evacuation of the treated fumes into the atmosphere or, alternatively, if further washing or filtering operations are required for the removal of the residual pollutants and liquid fraction, with a second filtration and depuration stage, consisting for example in a known "plate washing tower 3".

Being well known to those skilled in the art, it will not be necessary to dwell for a long time on the characteristics of such washing towers 3 or similar devices. It should be reminded only that they consist of vertical devices 3 characterised, internally, by the presence of various perforated supports 30 with horizontal setup, the so-called "plates" 30, capable of being crossed by a washing liquid from top to bottom and in countercurrent from the flow of fumes to be treated; the liquid loaded with the pollutants subtracted from said fumes flows inside a second and dedicated collection and decantation tank 31 obtained in the lower part or base 32 of the tower 3.

According to a possible construction variant, nothing prevents said tank 31 of the washing tower 3, where present, from being integrated and forming a single body with the tank 23 of the wet-wall scrubber 2.

A fan 24, preferably located at the inlet of the loading zone 20, has the task of ensuring the circulation of the combustion fumes exiting the combustor by overcoming the load losses along the fumes treatment system 1 of the invention. More precisely, the input pressure of the fan 24 coincides with the output pressure of the combustion fumes at the head of the combustor, normally close to the ambient pressure, whereas downstream of the same the delivery pressure must preferably be at least equal to the losses expected through the wet-wall scrubber 2, the stack, the possible washing tower 3 and the relative ducts and connection fittings.

Said fan 24 may also be equipped with a motor controlled by inverter with feedback of the number of revolutions of its impeller 240 for adjustment of the flow rate and of the speeds of the fumes to be treated.

Once the wet-wall scrubber 2 of the invention has been generally described, let's now proceed to describe a possible executive embodiment thereof, which is, without any limiting intent, among the preferred ones.

As schematically shown in Fig. 6, said loading zone 20 may comprise a first duct 200, directly connected to the fan 24 and capable of being crossed by the fumes F to be purified, and a chamber 201.

Said first duct 200 and said chamber 201 are preferably coaxial to each other, with said outer chamber 201 crossed by the same duct 200.

The outlet mouth 204 of said first duct 200 and that 205 of the outer chamber 201 (which in the example corresponds to an annular section) insist on and flow into the mixing zone 21 of the scrubber 2.

According to the invention, the annular chamber 201 is designed to collect and convey towards said mixing zone 21 the combustion ash C intentionally taken, for example, from a containment space of the combustor or from special temporary storage areas. From here on, said chamber 201 will be referred to as "conveying chamber 201 ".

The summit area 201.S of the conveying chamber 201, preferably of cylindrical geometry, comprises at least one inlet 202 of the ash, the latter being carried at high speed by an adjustable flow of compressed air, which therefore acts as a "carrier".

Special pipes 203 connect the ash space of a combustor or the storage area of the same to the relative inlet 202 of the conveying chamber 201.

As clearly visible in Fig. 5b, each pipe 203 preferably engages "tangencially" in said summit zone 201.S of the conveying chamber 201 so as to impart that swirling motion to the ash and compressed air flow; an ash flow C that from its summit zone converges with swirling motion towards the discharge annular outlet 205 is therefore generated inside the conveying chamber 201.

Such swirling motion eases, as already said, the mutual impact among ash particles among ash particles C, sometimes of large dimensions and/or diameters, and possibly with the dusts already suspended in fumes F and/or with the walls in the conveying chamber 201, favouring that crushing and pulverisation previously described.

Preferably, the conveying chamber 201 has a truncated-cone geometry along it longitudinal development and provides a convergent portion between its summit zone and the outlet mouth 205, necessary to speed up the ash flow C.

It has been experimentally found that such acceleration further favours the above-mentioned impacts, as well as a more intimate mixing of the ash C with the combustion fumes in the underlying mixing zone 21.

Said mixing zone 21 comprises a mixing chamber 210.

A conveyor 211 connects said mixing chamber 210 to the underlying washing zone 22 where, as anticipated, the cleaning and treatment of the combustion fumes as well as their dehumidification is carried out.

Preferably, also said conveyor 211 is a portion of converging duct that accelerates the fume-ash mixture F+C of the mixing chamber 210 and favours its passage in the washing zone 22.

As shown schematically in Fig. 6, the flow of fumes and ash F+C spreads inside the space 220 of said washing zone 22 with a preferably truncated-cone pattern. According to a preferred construction variant, said space 220 is defined among: - side walls 221, - a bottom 222 suitably communicating at the bottom with at least the said decantation tank 23 of the washing residues R and sludge M,

- an upper cover 223 cooperating with an inlet chamber 224 for the washing water.

Advantageously, said washing zone 22 may consist of a tubular body 220 with cylindrical geometry crossed from top to bottom by said flow of fumes and ash F+C and by at least one flow of washing water, in equicurrent.

At least one slit 228 (see Fig 6 and/or 5c) obtained in the cover 223 enables the passage of the washing water from the inlet chamber 224 to the space 220 of the washing zone 22.

Preferably, said slit 228 may consist of a circular slit, shaped and sized so as to generate a corresponding water cylinder or washing fluid that intercepts and intersects the flow of the fume-ash mixture F+C, for the reduction of suspended dusts and/or ash.

Preferably, said at least one circular slit 228 may consist of a plurality of slits 228 concentric to each other.

This enables generating a corresponding plurality of washing water cylinders, also concentric, which allow a more effective cleaning of the fumes.

In fact, as can be understood from the schematisation of Fig. 6, the outermost and most distant water cylinders relative to the vertical axis X-X of the scrubber 2 of the invention are able to intercept those particular polluting particles and ash that may "detach" from the main flow F+C and/or not being captured and reduced by the innermost cylinders.

Although non shown in the attached figures, nothing prevents the possibility of providing at least one additional slit in the proximity of the inner walls 221 of the space 220 so as to generate a further water cylinder which, by touching the same walls 221, avoids the fouling thereof and the formation of encrustations.

Nothing prevents one or more slits 228 from having alternative geometries and arrangements to those described so far.

For example, said slits 228 may consist of simple slots, variously shaped, which can intersect to define suitable lattices; typically, said slots create water blades or washing "cascades".

As shown in Fig. 5b and/or 5c, said inlet chamber 224 comprises at least one inlet 225 for the washing water drawn by the pipes from the water mains, by suitable basins or, without any limiting intent, by sections downstream of the waste-to-energy plant; for example by the collection and decantation tank 31 of the washing tower 3 or, as shown by way of an example in Fig. 1, by the decantation tank 23 of the scrubber 2; it is obvious that the washing water draw from the decantation tanks 23 and/or 31 requires an accurate and complete stratification of the residues and sludge stored, with the solid fraction precipitated on the bottom thereof so as to leave the upper layers sufficiently clarified and usable for the purpose.

In this configuration, a pump 5 regulated by inverter, draws the washing fluid A from the upper part of the tank 23 and conveys it through the pipe 226 to the wet-wall scrubber 2, said pipe 226 comprising at least one sensor for the measurement of the flow rate and/or sensors for detecting the chemical/physical characteristics of the fluid A (such as pH meters, conductometers, thermometers, etc.).

227 (see Fig. 6) indicates the loading section of the fumes treated and intended for a further treatment, for example in said washing tower 3 and/or for the direct disposal in the atmosphere by stack 33. Said fume discharge section 227 is preferably positioned in the proximity of the decantation tank 23; in such way, in fact, the fumes can touch the "cold" surface of the washing residues and of the sludge contained therein and condensate the wet component possibly still present.

Even for the washing water A, there may be provided an inlet substantially "tangential" in said chamber 224, which preferably has circular section and cylindrical geometry, so as to impart it an advantageous swirling-turbulent motion.

Experimentally there has been found that said swirling-turbulent motion may lead to a rotation with respect to the vertical axis x-x of the scrubber 2 by at least the initial portions of said one or more washing water cylinders or blades, which eases the interaction with the fumes and ash flow F+C.

Preferably, the rotation direction imparted by the washing water is contrary to that of the ash flow inside the conveying 201 and/or mixing 210 chamber, such condition further amplifying said interaction and the consequent reduction of particulates, pollutants and the same ash, suitably hydrated.

For such purpose, as clearly shown in Fig. 6, the inlet pipes 203 and 226 for the ash C and the washing water A are positioned and engaged in the wet-wall scrubber 2 of the invention so as to guarantee said contrary rotation directions to the respective fluids.

At least for a construction variant, it is possible to provide in the above- mentioned conveying chamber 201 of the ash and inlet chamber 224 of the washing fluid a plurality of relative inlets 202, 225.

Preferably, there may be provided three or more inlets equally spaced to each other.

This configuration, although constructively more complicated, can assure greater turbulence and vorticity of said ash and/or washing fluid, amplifying the advantages previously described.

It is clear that several variants of the invention described above are possible for the man skilled in the art, without departing from the novelty scopes of the inventive idea, as well as it is clear that in the practical embodiment of the invention the various components described above may be replaced with technically equivalent ones.

For example, nothing prevents the same functional groups described above, in particular at least the above-mentioned summit zone 201.S of the conveying chamber 201 and/or the space 220 of the washing zone 22 and/or the relative inlet chamber 224 for the washing fluid A, from being obtained in a prismatic rather than cylindrical form; in such case, the swirling motion of the ash flow and compressed air and of the washing fluid become substantially linear flows. Furthermore, nothing prevents that in place of the above-mentioned slits 228 of the cover 223 of the washing zone 22 of the wet-wall scrubber 2 of the invention special nozzles or similar means adapted to the generation of nebulised and atomised water jets may be provided that can replace, from a functional point of view, the above-mentioned cylinders or washing water blades.

A further simplified variant of the invention may be achieved by simultaneously injecting the ash C and the washing fluid A at the same level (same height) in the scrubber 2; e.g., it is possible to provide a simplified configuration in which ash C and washing fluid A are both conveyed from the respective inlet pipes 203 and 226 at the above-mentioned loading zone 20 of the wet-wall scrubber 2 of the invention.

In the decantation tank 23 of the scrubber 2 of the invention as well as in that 31 of the possible subsequent plate washing tower 3 special sensors and possible mixing/agitator devices 4 (see Fig. 3) may be provided, adapted, for example, to constantly detect the level of the washing residues and sludge accumulated and/or to monitor in real time their chemical-physical characteristics.

By way of a non-limiting example, said sensors may comprise level sensors, pH meters or conductometers or the like.

In conclusion, it is clear that with the wet-wall scrubber 2 of the invention the intended objects are achieved, in particular that of providing a system for the treatment of the products and fumes deriving from the combustion of combustible material, preferably biomasses or poultry dejections, able to reduce as much as possible the polluting emissions and the consequent dispersion in the atmosphere of dustlike and contaminant material.

The fumes are also discharged into the atmosphere with a very low value of absolute humidity.

As seen, said fume treatment system comprises a reduced number of functional components, of reduced overall dimensions and high efficiency and inexpensiveness. Thanks to the complete integration of the fume treatment and ash treatment, an extremely more compact plant than the prior art is obtained. Finally, said system 1 enables an effective recycling of the combustion ash that, instead of being disposed of in the landfill, can be suitably hydrated and transformed into sludge without the need of dedicated equipment, so as to be made compatible with future preparation work for an alternative use thereof, for example for the preparation of fertilisers.

Said ash may be therefore considered as fully recoverable and recyclable resources; moreover, can be forcibly introduced and used in said system for the treatment of the combustion fumes for a better cleaning and dehumidification thereof.